1. Field of the Invention
This invention relates broadly to prostheses and devices for use therewith. This invention particularly relates to ophthalmologic prostheses, and more particularly to medical canalicular inserts such as punctum plugs, and inserters therefor.
2. State of the Art
The surface of the eye and the inner surface of the eyelid are moisturized by tears constantly produced by glands around the eye. A tiny hole, known as the lacrimal punctum, located at the medial margin of each upper and lower lid margin drains the tears away through ducts for proper circulation.
A variety of eye problems are related to an insufficient volume of tears on the surface of the eyes. The most common is keratoconjunctivitis sicca, also known as dry eye syndrome. A common cause for the insufficient tear volume is the drainage of tear fluid through the punctal opening, the lacrimal duct, and into the nasal passage, thereby removing the fluid from where it is needed at the eye surface. Contact lens wearers particularly suffer when there is a lack of tear volume. In addition, dry eye is a component of various ocular surface diseases such as corneal ulcers, conjunctivitis, pterygium, blepharitis, keratitis, red lid margins, recurrent corneal erosion, filamentary keratitis and other external eye diseases.
A number of methods for closing the punctal opening have been used to prevent dry eye, including suturing, laser sealing, and plugging. Plugging with a punctum plug is the least severe solution, is relatively inexpensive, and is being performed with increasing frequency.
In addition, punctum plugs may be useful in decreasing contact lens intolerance, for increasing retention enhancement of ocular medications on the eye, for maintenance of ocular flora, for punctal stenosis, and to enhance healing and comfort after surgery.
A punctum plug typically includes an elongate shaft having a proximal end and a distal end, a head at the proximal end of the shaft, and a relatively larger body at the distal end of the shaft for occluding a lacrimal punctum. The plug is usually provided with a proximal axial bore for receiving an insertion tool. In the current punctum plug insertion procedure, the sphincter muscle about the punctal opening is dilated with a dilator and an insertion tool, on which the plug is mounted, is used to maneuver the plug towards the dilated punctum. Force is then applied to the insertion tool to move the body of the plug through the punctal opening, the muscles of the punctal ring, and into the vertical punctum of the lacrimal canaliculus until the plug is fully inserted. The plug is fully inserted when the head seats against the tissue at the punctal opening and the body seats within the lacrimal punctum and vertical canaliculus so as to block the passage of tear fluid into the punctum and thereby retain tear fluid at the surface of the eye.
Once the plug is fully inserted in the punctum, the insertion tool is decoupled from the plug and withdrawn. The insertion tools can be categorized as passive or active. Passive tools have no moving parts, while active tools are actuated to move a plug mount portion of the tool relative to the plug in order to disengage the plug mount from the plug.
Prior art passive tools generally comprise a cylindrical wire element coupled to a relatively larger handle element. The insertion tool is removed from the plug by wiggling the inserter relative to the plug or while stabilizing the plug with forceps and applying a withdrawal force to the tool until the plug and tool are decoupled. Such insertion tools are disclosed in U.S. Pat. Nos. D295,445, 3,949,750, and 5,283,063, all to Freeman, U.S. Pat. No. 4,915,684 to MacKeen, U.S. Pat. No. 5,423,777 to Tajiri, and U.S. Pat. No. 5,723,005 to Herrick. While such tools are inexpensive to manufacture, they provide less than desirable control for release of the plug. In fact, the wiggling motion required to disengage the tool from the plug may inadvertently remove the plug from the punctum or relocate the plug to a less desirable portion of the punctal anatomy.
The more complex active insertion tools, when actuated, provide a single instrument which applies relative forces to the plug and the tool, e.g. by stabilizing the plug and withdrawing the inserter or by stabilizing the inserter and advancing the plug off the inserter. An exemplar active insertion tool is shown in U.S. Pat. No. 5,741,292 to Mendius. That tool includes a cylindrical body having an elongated button arranged longitudinally along the body. The button includes a slidable end and a fixed end positioned between the slidable end and a plug mounting end. The button has an outwardly bowing inner surface spaced from the body such that when the button is pressed toward the body, the slidable end slides away from the plug mounting end. A wire is fixedly attached to the slidable end of the button, and slidably extends within the body and protrudes out of the plug mounting end. A punctum plug is attached to the protruding end of the wire. When the button is depressed, the wire is retracted to release the plug.
Another active tool is provided by FCI Ophthalmics of Marshfield Hills, Mass. with its Ready-Set™ punctum plug system. The insertion tool is generally similar to the device described in U.S. Pat. No. 5,741,292, but includes a two-sided releasing mechanism with handles located on diametrically opposite sides of the body. When the handles are pressed toward each other, the plug mounting end of the tool moves relative to the wire and forces the plug off the wire, thereby dislodging the plug from the mount.
While the tools described in U.S. Pat. No. 5,741,292 and available from FCI Ophthalmics are effective for punctum plug insertion, such tools are significantly more expensive to manufacture than the passive tools. Moreover, as the active tools include moving parts, they can be more prone to malfunction than the passive tools.
Furthermore, in current plug implantation systems, it is not uncommon for plugs which are inappropriately sized for a particular punctum to be implanted. For example, punctal dilation tends to permit plugs that are too large for a particular punctum to be inserted therein. Then, once the punctal opening reassumes its natural size, the plug may cause irritation to the recipient. In addition, the stress of a plug too large for the particular punctum may undesirably permanently stretch the punctal anatomy. In addition, it is not uncommon for plugs which are too small to be inserted into a punctum and released from either an active insertion tool (by actuation) or a passive insertion tool (e.g., by stabilizing the plug head with a tool and wiggling the instrument away from the plug). If a plug is too small for the punctum into which it is implanted, it will likely be prematurely extruded, often within days of implantation. Thus, without specifically gauging the size of the punctum prior to insertion, none of the prior art systems provide a desirable way of releasing a plug which is appropriately sized for a given punctum.